Method of quenching and cooling vapors



Jan. 28, 1941. QEKLEIBER my 2,414,817

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on. MAKE UP Patented Jan. 28, 1947 METHOD or QUENCHING AND COOLIN vAroas Carl E. Kleiber, Irvington, Donald L. Campbell, Short Hills, and Daniel E. Stines, Elizabeth, N. J., and George T. Atkins, Highlands, Tex., assignors to Standard Oil Development Company, a corporation of Delaware Application November 13, 1943, Serial No. 510,204

2 Claims. (Cl. 260-6815) The present invention relates to improvements in the dehydrogenation of normally gaseous hydrocarbons catalytically in a continuous operation under closely controlled conditions of time, temperature, and pressure, and in particular it relates to a method of quenching the reaction products to prevent decomposition or degradation of desired constituents in t e product stream.

In the application of Carl E. Kle ber et a1., Serial No. 486,636, filed March 12, 1943 there is described a process and apparatus for dehydrogenating hydrocarbons such as butene one of the outstanding features of that process being that the dehydrogenation is carried out in the presence of a greater volume of steam than reactants in order to lower the partial pressure of the reactants and thereby counteract the tendency for polymer formation and to otherwise improve the operation.

We are enabled to so operate because we employ a catalyst which is not aifected by steam. There also is disclosed in the aforesaid application the feature of two-stage quenching of the hot reaction products, and in this present applioperation characterized by what might be con- 7 sidered to be three phases, as follows: First, desuperheating of the reaction products issuing from the reaction zone; (2) condensation of the tar-forming and gum-forming constituents; and (3) gas cooling and water condensation.

One important result of this operation is that we avoid -simultaneous tar and water condensation with its attendant emulsification problems and the further problem of removing objectionable matter from the water so that it may be discharged into riparian streams. More particularly, we first desuperheat the hot reaction products by an initial water quenching operation followed by abstraction of heat in a waste heat boiler, or the like. We then quench with oil to a point below the dew point of tar components but above the condensation temperature of water and finally after separation of the tar or gummy constituents we cool the gases sufiiciently to condense the steam.

It is the main object of our invention therefore to quench hot raw butadiene reaction products with oil under conditions such that tar and gum-forming constituents are condensed, but substantial quantities of steam are not condensed.

A more specific object of our invention is to provide a process for quenching hot reaction products as soon as possible after their formation to prevent their degradation or decomposition, which tends to occur at the high temperature level of their formation, by quenching the products with liquids, including water, by a method which avoids oil-Water emulsion formation, and its attendant undesirable consequences.

In the accompanying drawings we have shown in Figures 1 and 2apparatus in which. preferred modifications of our invention may be carried into practical eflect.

In describing a method illustrating a preferred modification of our invention, we shall assume that butadiene containing vapors are the reaction products to be cooled and that the same have been formed by dehydrogenation of 'butene by some suitable method such as that described in the aforementioned application. Hence refer.. ring in detail first to Fig. l, i represents the reactor in which the butadiene is formed. We have assumed that thereaction products flow downwardly through the reactor containing the catalyst and are withdrawn from the bottom through a pipe 5. Just prior to withdrawal of the reaction products and immediately after their issuance from contact with the catalyst, they are quenched within the reactor by the injection of liquid water at ordinary atmospheric temperature through a line 3 projecting into the reactor and releasing the water through nozzles 4 or any other suitable distributing device. The reaction products are cooled by the water quench just now referred to from a temperature of approximately 1100 to 1250 F. to a temperature within the range of from about 900 to 1000 F. The purpose of this original quench, accomplished virtually at the moment of the egress of the vapors from the catalytic zone, is to reduce the temperature of the reaction products containing butadiene to a temperature level at which the tendency for polymerization to occur is greatly minimized, and, as indicated, this water quench is accomplished immediately so asto reduce rapidly the reaction temperature.

Thereafter, in order to recover for some usein] purpose a substantial quantity of the sensible heat contained in the reaction vapors, the same are passed from line 5 through a waste heat boiler l0 where the temperature of the vapors is reduced to temperatures within the range of from about 500 to 600 F. and, of course, the heat represented by this temperature reduction maybe utilized to improve the economics of the process .The next phases of our operation involve twostage quenching. in the first stage of which the vapors are quenched with an oil to a temperature which is sufficiently low to permit condensation of oils and tarry products but high enough to prevent substantial condensation of steam, To-

through line 64 into the top of the oil quench tower and over suitable contacting means such as the three bubble cap trays shown in the drawings.

The cold oil which is at about atmospheric temperature in line I2 serves to cool the reaction products to a temperatureof about 300 F. whereupon they. are withdrawn through line 25 and passedto a second and final cooling stage which shall be described presently. The bottoms constituting the quench oil are withdrawn from the tower 20 through line 30, thence umped by pump 32 through a heat exchanger 35 and thence recycled via line l2 'at the temperature previous y indicated to the quench tower 20. In quench tower 20, during the operation we have just now described, oil and tarry polymers are condensed and to remove these from the system we provide for them a draw-off line 40. A corresponding amount of clean purging oil is introduced into the circulatory system through line 45.

Referring again to the reaction products, in line-25, the same are discharged into the heat exchanger 50 where their temperature is reduced to about 185 F. and thence they are discharged by line 52 into a water quench tower 55, Overhead from water quench tower 55, the butadienecontaining product is withdrawn through line .60 and delivered to storage (not shown).

Cooling water is charged to the top of the water quench tower through line 68 and this cooling water together with the steam it condenses are withdrawn from the water quench tower 55 through line 62 and the said water and condensate are substantially free of tarry polymers or other contaminants which would make it an undesirable waste liquor to discharge into a natural stream or river. Minor quantities of light gas oil may condense in the tower 55 but they'do not emulsify with the water. They form a separate layer which may be drawn off through line 63.

We shall not describe a method of purifying the butadiene nor have we illustrated this procedure in the drawings because those features do not go to the heart ofour invention. Numerous processes are available for treating the raw butadiene with suitable selective solvents to extract it from unconvertedbutylenes and other contaminating normally gaseous hydrocarbons. Not shown in the drawings are. stripping means of any suitable type well known to the art which may be employed to strip and vaporize any butadiene in the-oil withdrawn through line 40 and the water withdrawn through line 62. The butadiene thus vaporized is returned as a. vapor to the bottom of oil quench tower 20 or water quench tower 55 respectively,

As to the internal design of the oil quench tower 20 this can be advantageously modified according to circumstances. Thus, for example, a conventional countercurrent tower with bell cap plates has been successfully employed, giving great intimacy of contact and a close. control over the final temperature of the gaseous product.

Bafiie plates, especially of the disc and doughnut type, may be substituted for the bell cap. plates;

and it will be desirable to do so in cases where tars and polymers tend to deposit and tojblcck up the narrower passages of the bell caps. In

certain cases where it becomes particularlyv desirable to avoid overheating of the liquid phase, and the resulting polymerization of dissolved tar forming components, a concurrent downward flow over disc and doughnut baffies will become desirable. The downward concurrent flow is accomplished by introducing hot gases from the preliminary cooling step into the top of theoil quench tower, immediate y causing the hot gases to mix' withcold quench oil also introduced at the top, and causing the mixture of gas and liquid to flow downward through disc and doughnut plates until themixing is substantially complete and the gases are cooled to a temperature approaching the condensation point of water.

In Fig. 2 we have shown a second exemplification of our invention, and at the outset we wish to point out that in this exemplification the essential difference from the exemplification of Fig. 1 is that in the oil quenching zone, the flow of gaseous reaction products is concurrent downtubes around which cooling Water circulates so that the metal within the quenching zone is continuously cooled.

Referring in detail toFig. 2, we shall assume that the' butadiene-containing vapors to be quenched have undergone the original quenching described in Fig. 1 and the sensible heat abstracted to the point wherethe vapors are .cooled in line II of Fig. 1 'to a temperature of 500 to 600.

F. In Fig. 2, the vapors in line II--a therefore are at about the same temperature as the vapors inline II of Fig. 1, that is, somewhere in the range of from 500-600 F. At this temperature we inject water into the vapor line II-a from line I-a, this water being at a temperature of about atmospheric and thereafter the vapors are discharged into an oil quenching zone 20a where it is mixed with oil introduced through line I2a and spray from nozzle ID. The quenching zone'2II-a contains a bank of tubes I00 terminating in tube sheets IOI, the tubes being in communication with the spaces above and below the said tube sheets. The mixture of quenching oil, water and hot gases pass concurrently downward through the tubes I00 and at the same time indirect cooling water is injected via line I II into the space between the tube sheets and surrounding the bank of tubes, the cooling water being withdrawn from 20'a through line H2. The quenched vapors and quenching oil are withdrawn from quenching zone 20a through line I02 and discharged into a separator I04 from which condensed tar may be withdrawn through line I60 carrying flow control valve and the former is withdrawn and gummy constituents carrying pu'mp I62 and then rejected from the system through line I80. Where gas oil is used to quench the vapors, and where it is not too contaminated with tar, a portion of the oil in line I 60 may be recycled through line I55 to coolers I10 and line Ill to line I2-a for further use in the process.

Referring again to the separator I04, it is pointed out that the liquid is maintained at a fairly constant temperature "of around 250 F. To insure thi temperature, I provide communication between the outlet line "I from the gas oil and tar coolers I10 by means of a line 205 206 which operates responsive to the temperature in I04 so as to admit cold oil to I04 automatically, to maintain the temperature level indicated. The overhead line I I5 contains the gases, namely the butadiene and steam, which are separated from the condensate in I04 and these are discharged into a second oil quenching zone 20-h, also fed with quenching oil from I2-b in precisely the same manner as in 20--a, and the cold oil flows downwardly through the tubes around. which cooled water from H0 circulates, and the gases are further cooled and quenched and eventually withdrawn through line I02--a and discharged into a second separator I04-a. As before; the separation is effected between the oil and the gases through line I00-a carrying pump I62-a, by means of which the oil maybe pumped from the system through line I80-a or recycled in part through line I05, as previously indicated.

with respect to the gases in separator l04-a, the same may bewlthdrawn through line I20, passed through coolers I22 and thence discharged into receiving drum I30 which we have shown tilted, via line I25. In steam is condensed together with light naphtha, and these condensates stratify in receiving drum I30, the water of course forming the lower layer, and this may be withdrawn through line I42 and rejected from the system through line I42. This water is substantially unpolluted with tar and may be discharged into natural stream or rivers. A portion of this water may be pumped by pump 200 and line 20I to the aforementioned line 1-41, which it will be recalled was a line supplying quench water to the vaporsabout to enter the first oil quenching zone.

Referring again to receiving drum I00, the

' naphtha maybe withdrawn through line I40 and rejected from the system. The butadiene-containing product is withdrawn from line I50 and thereafter purified by means not shown, since the solvent extraction and other conventional means of purifying butadiene do not go to the heart of this present invention.

Instead of causing the vapors and oil to flow concurrently downward in the quenching zones 20-a, the same may be caused to flow in such a manner that a portion of the vapors flow concurrently with the 011, while another portion flows counter-currently with the oil. We have notillustrated this modification of our invention in the drawings because suitable apparatus for accomplishing this result will be apparent to. those the gas coolers I22 the applicable to condense stea 'said product to cool of about 900 to 1000" familiar with the art in view of preceding description.

While we have described our invention in terms of butadiene quenching immediately following its formation during dehydrogenation of butenes it will be understood that our improvements are the quenching of any gaseous and or vapor product rapidly and immediately after its formation. In other words, our improvements are applicable broadly to the rapid quenching of newly formed reaction products which are, at high temperatures and which are apt to undergo degradation wtih consequent loss in yield to a point where such degradation is greatly minimized. And morespecifically, an important phase of our invention involves the quenching of oily material or hydrocarbon material at high temperatures admixed with water under conditions such that the main body of the water is condensed uncontaminated with substantial quantities of oily material or with merely minor quantities of light oily material and substantially free of tarry and heavy material.

What we claim is: i

1. In the production of diolefins by catalytic dehydrogenation of relatively more saturated hy: drocarbons in the presence of steam to form a gaseous product stream containing said diolefin, steam and unstable tar-forming and gum-forming impurities, an improved method of cooling said product stream to prevent degradation of the desired diolefln, comprising withdrawing said product from the reaction zone, immediately injecting water into said product to cool it quickly to a temperature of 900 to 1000" l? then cooling the product by indirect heat transfer to a temthe product by direct contact with a liquid hydrocarbon oil to a temperature of about 300 F.

to remove said tar-forming and gum-forming impurities, th n further cooling said product to therefrom by direct contact with liquid water, and thereafter separating the resulting diolefln-containing product from the water condensate.

2. In the production, of butadiene by catalytic dehydrogenation of normal butenes in the presence of steam to produce a gaseous product stream containing butadiene, steam and unstable tar-forming and gum-forming impurities, an improved method of cooling said product stream, comprising withdrawing said product Ifrom the reaction zone, immediately injecting water into it quickly to a temperature F., then cooling the product by indirectvheat transfer to a temperature of about 500 to 600 1- then further cooling the product by direct contact with. a liquid hydrocarbon oil to a temperature of about 300 1". to remove said tar-forming and gum-forming impurities, then further cooling said product to condense steam therefrom, and thereafter sepgrating the resultingbutadIene-containing prodnet rrom the water condensate.

CARL E, KLEIBER. DONALD L. CAMPBHL. DANIEL E.

BTINEB. GEORGE T. ATKINS 

